Enabling cisco legacy power to support IEEE 802.3 AF standard power

ABSTRACT

An apparatus and method for enabling Cisco legacy power to support IEEE 802.3af standard power. A network power system capable of delivering data terminal equipment power via a media dependent interface (MDI) includes power source equipment according to a first power via MDI scheme such as Cisco legacy power and at least one powered device according to a second power via MDI scheme such as IEEE standard power. A power compatibility module is inserted between the power source equipment and the powered device to enable the power source equipment to appear according to the first power via MDI scheme and the powered device to appear according the second power via MDI scheme. In one embodiment, the module includes switches, a DC/DC converter, an IEEE power source equipment circuit, and an isolator. The module may optionally include a user signaling device for communicating operating conditions of the module to a user.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation application based on U.S. patentapplication Ser. No. 10/360,338, filed on Feb. 6, 2003 now U.S. Pat. No.6,912,282.

FIELD OF THE INVENTION

The present invention relates generally to a network power systemincluding power source equipment, at least one powered device, andtransmission media. More specifically, the present invention relates toa network power system including non-IEEE standard power sourceequipment and at least one IEEE standard powered device.

BACKGROUND OF THE INVENTION

In the field of networks, there are instances when it is desired orrequired that data terminal equipment (DTE) be able to draw power fromthe same generic cabling as that used for data transmission. DTE devicesmay include telephones, Voice over Internet Protocol (VoIP or IP orEthernet) telephones, network access devices, computers, and the like.Such a power scheme is known as phantom power or power via a mediadependent interface (MDI). Various example power via MDI schemes exist.These include a proprietary scheme from Cisco Systems, Inc. (Cisco) anda standard scheme from the Institute of Electrical and ElectronicsEngineers (IEEE). The proprietary scheme from Cisco will be referred toas Cisco legacy power. The IEEE scheme is known as IEEE 802.3af standardpower and will be referred to as IEEE standard power. Although the twoschemes have some aspects in common, they are not entirely compatiblewith one another.

Turning first to FIG. 1, a schematic diagram of a network power system10 having power source equipment (PSE) 12, a plurality of powereddevices (PD) 14A-N, and a plurality of corresponding transmission media16A-N is shown. The plurality of transmission media 16A-N are connectedto the corresponding power source equipment 12 and powered devices 14A-Nthrough a power interface at each end of the transmission media. Eachtransmission media may contain a plurality of conductors. For example,the current Ethernet standard is a minimum of two twisted-pair cablesfor a total of four conductors. The length and routing of thetransmission media will depend on the circumstances and the applicablecommunications protocol. The number and location of each of theplurality of powered devices 14A-N will depend on the circumstances. Thepower source equipment 12 may also be variously located based on thecircumstances. The multiple power interfaces of the power sourceequipment 12 are often referred to as ports. The number of ports willvary. Typically, one port is connected to one powered device. Themultiple transmission media are often referred to as links between thepower source equipment and the various powered devices. Each linkincludes at least two data and power signal paths with one fortransmitting and one for receiving. In order for the network powersystem 10 to operate correctly, the power source equipment 12 and theplurality of powered devices 14A-N must be compatible with one another.

BRIEF SUMMARY OF THE INVENTION

An apparatus and method for enabling Cisco legacy power to support IEEE802.3af standard power is disclosed. A network power system capable ofdelivering data terminal equipment (DTE) power via a media dependentinterface (MDI) includes power source equipment (PSE) according to Ciscolegacy power and at least one powered device (PD) according to IEEEstandard power. A power compatibility module is inserted between thepower source equipment and the powered device to enable the power sourceequipment to appear according to IEEE standard power and the powereddevice to appear according to Cisco legacy power. In one embodiment, themodule includes switches, a DC/DC converter, an IEEE power sourceequipment circuit, and an isolator. The module may optionally include auser signaling device for communicating operating conditions of themodule to a user. The module may be connected to two ports of the powersource equipment to supply adequate power levels to the powered device.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated into and constitute apart of this specification, illustrate one or more exemplary embodimentsof the present invention and, together with the detailed description,serve to explain the principles and exemplary implementations of theinvention.

In the drawings:

FIG. 1 is a schematic diagram of a network power system having powersource equipment, a plurality of powered devices, and a plurality ofcorresponding transmission media;

FIG. 2 is a schematic diagram according to Cisco legacy power of thepower source equipment as in FIG. 1;

FIG. 3 is a schematic diagram according to IEEE standard power of thepowered device as in FIG. 1; and

FIG. 4 is a schematic diagram of an embodiment of a power compatibilitymodule according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Various exemplary embodiments of the present invention are describedherein in the context of an apparatus and method for enabling Ciscolegacy power to support IEEE standard power. Those of ordinary skill inthe art will realize that the following detailed description of thepresent invention is illustrative only and is not intended to be in anyway limiting. Other embodiments of the present invention will readilysuggest themselves to such skilled persons having the benefit of thisdisclosure. Reference will now be made in detail to exemplaryimplementations of the present invention as illustrated in theaccompanying drawings. The same reference indicators will be usedthroughout the drawings and the following detailed descriptions to referto the same or like parts.

In the interest of clarity, not all of the routine features of theexemplary implementations described herein are shown and described. Itwill of course, be appreciated that in the development of any suchactual implementation, numerous implementation-specific decisions mustbe made in order to achieve the specific goals of the developer, such ascompliance with application- and business-related constraints, and thatthese specific goals will vary from one implementation to another andfrom one developer to another. Moreover, it will be appreciated thatsuch a development effort might be complex and time-consuming, but wouldnevertheless be a routine undertaking of engineering for those ofordinary skill in the art having the benefit of this disclosure.

In addition, one of ordinary skill in the art will recognize thatdevices of a less general purpose nature, such as hardwired devices,field programmable logic devices (FPLDs), including field programmablegate arrays (FPGAs) and complex programmable logic devices (CPLDs),application specific integrated circuits (ASICs), or the like, may alsobe used without departing from the scope and spirit of the inventiveconcepts disclosed herein.

In the context of the present invention, the term “network” includeslocal area networks (LANs), wide area networks (WANs), the Internet,cable television systems, telephone systems, wireless telecommunicationssystems, fiber optic networks, ATM networks, frame relay networks,satellite communications systems, and the like. Such networks are wellknown in the art and consequently are not further described herein.

Turning now to FIG. 2, a schematic diagram according to Cisco legacypower of the power source equipment 12 as in FIG. 1 is shown. In theinterest of clarity, only the pertinent portions of one power interfaceare shown. The remaining power interfaces are similar. The power sourceequipment 12 includes a power source equipment (PSE) physical layer 20,a network power controller (NPC) 22, an output power voltage (VPWR) 24,a switch 26, a PSE transmit (TX) magnetic 28, and a PSE receive (RX)magnetic 30. The NPC 22 monitors the output power voltage 24 andregulates the voltage level through the switch 26. The NPC regulatedpower is applied to the PSE transmit and receive magnetics 28 and 30.During data communication, a series of output data signals are generatedand a series of input data signals are received. The signals may besimultaneous or alternating. An output data signal is generated by thePSE physical layer 20 and applied to the PSE transmit magnetic 28 fortransmission to a powered device connected to the port. For example, thepowered device might be the first powered device 14A of FIG. 1 that isconnected to the power source equipment 12 by the first transmissionmedia 16A of FIG. 1. An input data signal that is generated by thepowered device connected to the port is received by the PSE receivemagnetic 30 and passed to the PSE physical layer 20. The power sourceequipment 12 performs many functions which may include searching thelink for a PD, supplying power to the link only if a PD is detected,monitoring the power on the link, and removing power from the link whenthe PD is disconnected. How these functions are performed differs fromCisco legacy power to IEEE standard power and accounts for some of theincompatibility between the two power via MDI schemes.

Turning now to FIG. 3, a schematic diagram according to IEEE standardpower of the powered device 14 as in FIG. 1 is shown. Similar to above,only the pertinent portions of the power interface are shown. Thepowered device 14 includes a powered device (PD) physical layer 32, anIEEE PD integrated circuit (IC) 34, a power converter 36, a firstcapacitor C1, a second capacitor C2, a PD RX magnetic 38, and a PD TXmagnetic 40. The IEEE PD IC 34 is a chip that performs the PD functionsof the power scheme according to IEEE standard power. During datacommunication, a series of input data signals are received and a seriesof output data signals are generated. The signals may be simultaneous oralternating. An input data signal that is generated by the power sourceequipment is received by the PD receive magnetic 38 and passed to the PDphysical layer 32. An output data signal is generated by the PD physicallayer 32 and applied to the PD transmit magnetic 40 for transmission tothe power source equipment. The IEEE PD IC 34 receives the input phantompower over the link and passes it to the power converter 36 whichgenerates one or more power levels. The power level may depend in parton which classification of device the powered device 14 is according toIEEE standard power. IEEE standard power has a number of predefinedpower classes and Cisco legacy power does not. This representspotentially one more of the incompatibilities. However, PDclassification is not strictly necessary at this time. Nevertheless, thepower demands of some of IEEE power classes may be beyond the powersupply capabilities of the power source equipment according to Ciscolegacy power which does represent an incompatibility between the twopower schemes. The various incompatibilities of the power sourceequipment according to Cisco legacy power and the powered devicesaccording to IEEE standard power can substantially be addressed.

Turning now to FIG. 4, a schematic diagram of an embodiment of a powercompatibility module 50 according to the present invention is shown. Themodule 50 is inserted into the link between the power source equipmentand the powered device. One convenient location would be closely beforethe powered device. It would also be possible to incorporate the module50 into the powered device making the powered device both Cisco legacypower and IEEE standard power compatible. Rather than one module 50 foreach powered device, it would also be possible to combine severalmodules 50 together. The module 50 includes switches 52, an optionalfilter 54, a DC/DC converter 56, an IEEE power source equipmentintegrated circuit (PSE IC) 58, an isolator 60, six capacitors C4-C9,eight inductors L1-L8, and an optional LED 1. The switches 52 andoptional filter 54 play roles in how the power source equipmentaccording to Cisco legacy power detects a compatible phantom powereddevice using differential mode signaling. The switches 52 are controlledby the IEEE PSE IC 58 which is a chip that performs the PSE functions ofthe power scheme according to IEEE standard power. The switches 52 andthe IEEE PSE IC 58 work together to enable the power source equipmentand the powered device to work together. The switches 52 help to makethe powered device according to IEEE standard power to appear as apowered device according to Cisco legacy power. Likewise, the IEEE PSEIC 58 helps to make the power source equipment according to Cisco legacypower to appear as a power source equipment according to IEEE standardpower. The isolator 60 works with the IEEE PSE IC 58 in accordance withIEEE standard power. The DC/DC converter 56 performs functions such asboosting the input phantom power voltage and isolating the input fromthe output. Depending on the circumstances, it may be the case that thevoltage level supplied by the power source equipment according to Ciscolegacy power is too low for the power class of the powered deviceaccording to IEEE Standard power. The DC/DC converter 56 may correct forthe under voltage condition. The optional LED 1 could be employed as auser signaling device to signal various operating conditions of themodule 50 to the user. The LED states of on, off, or flashing could beused to indicate proper or improper functioning. For example, the offstate might indicate no power flow, the on state might indicate powerflow, and the flashing state might indicate insufficient or intermediatepower flow. More than one LED might also be provided to further indicatevarious link conditions such as short or open.

As mentioned above, the power demands of some of the IEEE power classesmay be beyond the power supply capabilities of the power sourceequipment according to Cisco legacy power. One solution is to decline tosupport such power classes. In this case, the optional LED 1 might beused to signal the user that the module 50 is unable to power theconnected powered device. Another solution is to combine the power oftwo ports from the power source equipment. This can be accomplished byconnecting two ports to the input of the module 50 and one powereddevice to the output of the module 50. In this case, the optional LED 1might be used to signal the user that the power demand at the output ofthe module 50 is actually greater or is classed to be greater than thepower supplied at the input of the module 50. This would indicate to theuser that if only one input is connected, then a second input might benecessary. The power supplied by two ports should be sufficient for anyof the power classes that are compliant with IEEE standard power.

As an alternative to the embodiment of FIG. 4, it would be possible tochange control of the switches 52 from the IEEE PSE IC 58 to the user.In such a case, the control line to the IEEE PSE IC 58 could be deletedand an on demand user control such as a button would be added. Toestablish power, the user would press and hold the button that closedthe switches 52 until the LED 1 indicated that proper power was flowingto the PD. After proper power flow had been established, then the userwould release the button and thereby the switches 52 would return to anormally open position. As above, the filter 54 is optional.

As a further alternative to the embodiment of FIG. 4, it would bepossible to locate the DC/DC converter 56 inside of the powered devicerather than inside of the module 50. as shown. In such a case, the DC/DCconverter 56 and the capacitor C5 would be deleted from the module 50and the input of the IEEE PSE IC 58 would be connected across thecapacitor C4.

While embodiments and applications of this invention have been shown anddescribed, it would be apparent to those skilled in the art having thebenefit of this disclosure that many more modifications than mentionedabove are possible without departing from the inventive concepts herein.The invention, therefore, is not to be restricted except in the spiritof the appended claims.

1. A method for providing, by a power compatibility module,compatibility to a network power system having equipment capable of atleast two power via Media Dependent Interfaces (MDI) schemes fordelivering data terminal equipment power via an MDI, the network powersystem including power source equipment (PSE) configured to deliverpower via a first power via MDI scheme and a powered device (PD) coupledto the PSE and configured to receive power from the PSE via a secondpower via MDI scheme different from the first power via MDI scheme, themethod comprising: exchanging, by the power compatibility module,classification signals with the PD to classify a power class of the PD;in response to classifying the PD as an IEEE PD configured to receivepower according to an IEEE power classification, receiving, by the powercompatibility module, a power signal from the PSE at a first power levelaccording to the first power via MDI scheme and converting, by the powercompatibility module, the power signal to a power level corresponding tothe IEEE power classification of the PD, the power level correspondingto the IEEE power classification of the PD associated with the secondpower via MDI scheme; facilitating, by the power compatibility module,the PSE to operate according to the first power via MDI scheme whileappearing to the PD to be operating according to the second power viaMDI scheme; and facilitating, by the power compatibility module, the PDto operate according to the second power via MDI scheme while appearingto the PSE to be operating according to the first power via MDI scheme;wherein facilitating the PD to operate according to the second power viaMDI scheme while appearing to the PSE to be operating according to thefirst power via MDI scheme comprises forwarding, by the powercompatibility module, the power signal to the PD via the second powervia MDI scheme.
 2. The method as defined in claim 1, wherein the firstpower via MDI scheme is Cisco legacy power.
 3. The method as defined inclaim 2, wherein the second power via MDI scheme is IEEE standard power.4. The method as defined in claim 1, wherein the second power via MDIscheme is IEEE standard power.
 5. An apparatus for providingcompatibility to a network power system having equipment capable of atleast two power via Media Dependent Interfaces (MDI) schemes fordelivering data terminal equipment power via an MDI, the network powersystem including power source equipment (PSE) configured to deliverpower via a first power via MDI scheme and a powered device (PD) coupledto the PSE and configured to receive power from the PSE via a secondpower via MDI scheme different from the first power via MDI scheme, theapparatus comprising: means for exchanging classification signals withthe PD to classify a power class of the PD; in response to classifyingthe PD as an IEEE PD configured to receive power according to an IEEEpower classification, means for receiving a power signal from the PSE ata first power level according to the first power via MDI scheme andmeans for converting the power signal to a power level corresponding tothe IEEE power classification of the PD, the power level correspondingto the IEEE power classification of the PD associated with the secondpower via MDI scheme; means for operating the PSE according to the firstpower via MDI scheme while appearing to the PD to be operating accordingto the second power via MDI scheme; and means for operating the PDaccording to the second power via MDI scheme while appearing to the PSEto be operating according to the first power via MDI scheme; whereinmeans for operating the PD to operate according to the second power viaMDI scheme while appearing to the PSE to be operating according to thefirst power via MDI scheme comprises means for forwarding the powersignal to the PD via the second power via MDI scheme.
 6. The apparatusas defined in claim 5, wherein the first power via MDI scheme is Ciscolegacy power.
 7. The apparatus as defined in claim 6, wherein the secondpower via MDI scheme is IEEE standard power.
 8. The apparatus as definedin claim 5, wherein the second power via MDI scheme is IEEE standardpower.
 9. A network power system for delivering data terminal equipment(DTE) power via a media dependent interface (MDI), the systemcomprising: a power source equipment (PSE) configured to deliver powervia a first power via MDI scheme; a DTE adapted to receive power fromthe PSE via a second power via MDI scheme different from the first powervia MDI scheme; and a power compatibility module coupled to the PSE andthe DTE, wherein the power compatibility module is configured to:exchange classification signals with the PD to classify a power class ofthe PD; in response to classifying the PD as an IEEE PD configured toreceive power according to an IEEE power classification, receive a powersignal from the PSE at a first power level according to the first powervia MDI scheme and convert the power signal to a power levelcorresponding to the IEEE power classification of the PD, the powerlevel corresponding to the IEEE power classification of the PDassociated with the second power via MDI scheme; facilitate the PSE tooperate according to the first power via MDI scheme while appearing tothe DTE to be operating according to the second power via MDI scheme;and facilitate the DTE to operate according to the second power via MDIscheme while appearing to the PSE to be operating according to the firstpower via MDI scheme; wherein when facilitating the PD to operateaccording to the second power via MDI scheme while appearing to the PSEto be operating according to the first power via MDI scheme the powercompatibility module is configured to forward the power signal to the PDvia the second power via MDI scheme.
 10. The system as defined in claim9, wherein the first power via MDI scheme is Cisco legacy power.
 11. Thesystem as defined in claim 10, wherein the second power via MDI schemeis IEEE standard power.
 12. The system as defined in claim 9, whereinthe second power via MDI scheme is IEEE standard power.
 13. The methodof claim 1, wherein: facilitating the PSE to operate according to thefirst power via MDI scheme while appearing to the PD to be operatingaccording to the second power via MDI scheme comprises facilitating thePSE to deliver power according to the first power via MDI scheme whileappearing to the PD to be delivering power according to the second powervia MDI scheme; and facilitating the PD to operate according to thesecond power via MDI scheme while appearing to the PSE to be operatingaccording to the first power via MDI scheme comprises facilitating thePD to receive power according to the second power via MDI scheme whileappearing to the PSE to be receiving power according to the first powervia MDI scheme.
 14. The method of claim 13, comprising: receiving powerfrom the PSE according to the first power via MDI scheme, the powerreceived from the PSE according to the first power via MDI scheme havinga first voltage level; and delivering power to the PD according to thesecond power via MDI scheme, the power delivered according to the secondpower via MDI scheme having a second voltage level, the second voltagelevel being different than the first voltage level.
 15. The method ofclaim 14, comprising, in response to receiving power from the PSEaccording to the first power via MDI scheme, increasing a voltage levelof the power received from the PSE to the second voltage level, thesecond voltage level being greater than the first voltage level.
 16. Thenetwork power system of claim 9, wherein the power compatibility moduleis configured to: when facilitating the PSE to operate according to thefirst power via MDI scheme while appearing to the DTE to be operatingaccording to the second power via MDI scheme, facilitating the PSE todeliver power according to the first power via MDI scheme whileappearing to the DTE to be delivering power according to the secondpower via MDI scheme; and When facilitating the DTE to operate accordingto the second power via MDI scheme while appearing to the PSE to beoperating according to the first power via MDI scheme, facilitating theDTE to receive power according to the second power via MDI scheme whileappearing to the PSE to be receiving power according to the first powervia MDI scheme.
 17. The network power system of claim 16, wherein thepower compatibility module is configured to: receive power from the PSEaccording to the first power via MDI scheme, the power received from thePSE according to the first power via MDI scheme having a first voltagelevel; and deliver power to the DTE according to the second power viaMDI scheme, the power delivered according to the second power via MDIscheme having a second voltage level, the second voltage level beingdifferent than the first voltage level.
 18. The network power system ofclaim 17, wherein the power compatibility module is configured to, inresponse to receiving power from the PSE according to the first powervia MDI scheme, increase a voltage level of the power received from thePSE to the second voltage level, the second voltage level being greaterthan the first voltage level.
 19. The method of claim 1, wherein the PSEis configured to exchange data signals with the PD.
 20. The method ofclaim 15, wherein, in response to receiving power from the PSE accordingto the first power via MDI scheme, detecting the voltage level of thepower received from the PSE is lower than an amount of power required bythe PD according to a power classification of the PD; and in response todetecting, delivering power to the PD wherein the power has the secondvoltage level, the second voltage level being greater than the firstvoltage level.